Hydraulic coupling



June 11, 1940. w FRASER 2,204,261

HYDRAULIC COUPLING Filed Dec. 5, 1938 2 Sheets-Sheet 1 June 11, 1940. w s -ia 2,204,261

HYDRAULIC COUPLING Filed Dec. 5, 1938 2 Sheets-Sheet 2 FIG. 2."

l3 0/ I J in): IE :1 2a |@i Patented June 11, 1940 UNITED STATES 7 HYDRAULIC COUPLING William Fraser, Liverpool, England Application December 5, 1938, Serial No. 244,040

In Great Britain December 29, 1937 8 Claims.

This invention relates to hydraulic couplings of the type in which power is transmitted from a driving to a driven shaft through the agency of a series of cylinders and pistons rotated by one shaft, the pistons having rollers engaging a cam track carried from the other shaft and the reciprocation of the pistons during relative rotation of the shafts setting up a pulsating flow of fluid, such as oil, by way of ducts, such flow being controlled by a valve to effect any desired impedance and consequence variation in the hydraulic coupling grip between the driving and driven shafts. The present invention is an improvement on the mechanism of this type in which the pistons reciprocate in rotary balance and the cam is centrally disposed, the cylinders and ducts forming an outer enclosed compression zone separate from an inner reservoir zone from which the compression zone is replenished. m It is essential that the piston rollers should maintain contact with the cam in such couplings, which frequently have to run at very high speeds, and in the case of an inner cam the tendency of the pistons under centrifugal action to lose 26 cam contactwas avoided by intercontrolling them by means of levers. Also in couplings of this type where an exterior cam has been provided, difficulty was experienced in maintaining cam c'ntact because of the suction action developed 30 in the cylinders which set up a drag on the pistons preventing them freely moving out to follow the cam contour, and rigid spacing elements were provided between the pistons to constrain them to move outwardly in following the cam. The present invention is directed to a simplified construction of coupling of the exterior cam type whereby any such loss of cam contact is entirely prevented, without any necessity for levers or the like inter-controlling the pistons.

One embodiment of the invention is illustrated in the accompanying drawings in which:

Fig. 1 is a longitudinal medial section through the coupling;

Fig. 2 is an end view, the upper half in section on the line 22, Fig. 1, while the lower half shows the interior mechanism, the right-hand end plate of Fig. 1 being removed.

Fig. 3 is a detail partly in section, on a large scale, of one of the non-return valves for replenishing the pressure zone,

Fig. 4 being a detail section on a large scale of the air-relief valve to the pressure zone.

In the construction illustrated, the outer casing or reservoir comprises a cylindrical shell I formed with a cam track 2 on its inner surface,

the Shell be bolted at 3 between end plates 4, I one of which'is connected to the shaft 6, which may be the driven shaft. The end plates are fitted with roller or other bearings l, 8, and in one of these bearings 8 is journalled the other shaft 9, which may be the driving shaft. This is formed with a flange by which it is bolted at III to an inner casing H, the further side of which is fitted with a stub shaft I2 secured by the bolts l and journalled in the bearing 1 in the other end plate of the outer casing. Both shafts B and 9 are in alignment, and may relatively rotate. The inner casing is disc shaped and formed with a series of radially disposed cylinders l3, each provided with a piston i l having a roller i5 at its outer end adapted to ride against the cam track 2. Each piston is carried upon a transverse spindle l6 provided with cod or guide pieces ll at each side slidable in grooves I B in the cylinders. The purpose of these cod pieces is to meet oblique thrust set up on the pistons and rollers as the latter travel round the cam track. Packing rings l9 are fitted in the pistons.

Each cylinder is provided with an inwardly opening non-return valve 20, which is held closed by the pressure offluid in the cylinders when the pistons are moving inwardly on the pressure stroke but, when leakage of fluidoccursinthe compression zone 2|, is adapted to open inwardly on the outward movement of the piston. A duct 23 leads from each cylinder through the boss of the inner casing ii to a valve cavity 24 therein, the ducts terminating in ports in the cavity wall with which the ports 25 of a rotary cylindrical valve 26 cooperate to control their opening or closing and impede the flow between the cylinders. The stem 21 of this valve passes axially along a bore in the driving shaft 3, being packed at 28, and controlled for rotary movement by a fork engaging a channelled collar 29, the sliding movement of which on the shaft 9 effects angular movement of the valve in known manner by means of helical grooves 30 in the shaft and longitudinal grooves 3| in the valve stem 21, through the coincident parts of which grooves passes a pin 32 fixed in the collar 29. The valve 26 is rotarily secured on the valve stem 21 by forming a slot ll in the stem through which keys '42 are passed and engage grooves in the opposite faces 0 of the valve. When therefore the collar is slid along the shaft 9 the valve 26 will be turned and its ports brought more or less into register with the intercommunicating ducts 23 or entirely close them. The inner casing ii is provided with a i series of'radially or otherwise disposed impeller vanes 33 projecting laterally from such casing and adapted to deflect the non-pressure oil in the reservoir radially outwards. Nozzles 34 enclosable by plugs are provided for fllling the reservoir with oil.

In operation, the other reservoir zone 22 is supplied with oil while stationary to approximately the level indicated at 4-4, Fig. l, or such a quantity that when the coupling is rotating and the oil swirls centrifugaliy outward in the reservoir casing 22 assisted by the impeller vanes 33, the inner peripheral surface of the swirling oil will take up a position approximately indicated by the line 33, Fig. 1, and lie radially within the cylinder valves 20, which are thus always kept flooded. Small axial holes 35, Fig. 3, are formed in the stems of these valves open to the reservoir and communicating with small transverse holes 36 at the neck of the valve which lead to cavities 31 closable by the valve head when driving pressures prevail. When the valves lift under replenishment conditions, a quantity of oil may pass through the holes 35, into the cylinders to replenish any leakage which may have occurred in the pressure zone.

As it is essential in certain applications of the coupling that the oil in the inner pressure zone 2| should be kept free of any air content, which would otherwise render the mass in such zone compressible whereas the efliciency of the coupling is dependent upon the fluid in that zone being incompressible. means may be provided for permitting exit from that zone of any slight air content, though such a provision is not absolutely necessary as such central zone, for a reason to be explained later, will generally be free of air.

With this object, a very small air hole 38 is formed in the inner casing, such hole being controlled by a flap or other valve 39 and leading to a larger hole 40 in the stub shaft l2, and so communicating to the other reservoir. Should a slight air content be present in theworking zone, this air will, with some oil, be expelled by the compression action of the pistons it past the valve 39 into the reservoir and the air will not return through the valves 20 to the pressure zone because, due to the centrifugal action developed in the rotating oil in the outer casing and because of the difierent densities of air and oil, the latter will displace any air content in the reservoir to the central part thereof, so that the valves 20 being flooded by the swirl of reservoir oil, the air excluded from the pressure zone will not return thereto but will remain in the central part of the reservoir. ,Further, because of this centrifugal swirl of oil, none will lie in the central part of the reservoir round the shaft 9, and consequently the necessity for any elaborate packings for that shaft where it protrudes from the outer casing i and which have been requisite in previous hydraulic couplings is eliminated.

inner zone from that effective part of the fluid supply therein lying radially within the valves 20. Further, because of the expulsion of air and oil from the inner zone 2| by way of the ducts 38 and 40 to the reservoir 22, and the return of oil from the reservoir through the valves 20 to the inner zone, a continual change of oil in the pressure zone takes place.

The mechanism is capable of effective action when either of the shafts 8 or 9 is the driving shaft. The function of the impellers in the form illustrated is to assist the setting up of a rotary swirl of oil in the reservoir at starting speeds until the centrifugal action developed in the reservoir oil asserts itself and causes the mass of fluid to lie along the outer part of the reservoir, as previously explained. The action of the impellers would thus assist separation of the oil outwardly from the air initially. When the coupling is rotating, all the valves 20 will be submerged in the reservoir oil and thus be operative.

In some applications of the coupling it may not be necessary to provide impellers, but generally they would be desirable and where, as say in a lathe drive, the relative speeds of the driving and driven elements are subject to continual differentiation, the impellers would always be on the driving shaft to assist in setting up an initial swirl of oil in the reservoir. On the other hand in such applications where a difference in the speeds of the respective shafts practically occurs only at starting and the respective parts of the coupling ultimately and mainly rotate in unison, the impellers may be fitted in such manner that their effect at starting will be to churn up the oil and air content in the reservoir into a mixture which will fill into the pressure zone by the valves 20 and temporarily afford a resilient cushioning action to the pistons. After starting and owing to the normal cycle of loss from and return of oil to the pressure zone. this mixture of oil and air will soon separate out in the reservoir under centrifugal action, the oil in the pressure zone ultimately becoming free of air as the speeds of the driving and driven shafts approximate.

The contour of the cam'track and the number of pistons are so arranged that the pistons are always in rotary balance as they reciprocate.

imparting a more even ervoir, an inner casing on the other shaft rotarily mounted in the outer casing, a series of intercommunicating radially disposed cylinders and pistons in the inner casing forming an enclosed pressure zone within the reservoir, a valve controlling intercommunication between the cylinders, a. symmetrical cam formed on the outer casing, rollers on the pistons engaging the sym metrical cam whereby the pistons are reciprocated in,rotary balance, and non-retum valves in the cylinder walls located radially within the piston travel and adapted to open and permit,

fluid to pass from the outer reservoir to the inner pressure zone to replenish such zone only when leakage occurs therein.

2. In a hydraulic coupling as claimed in claim 1, impeller vanes mounted on the inner casing said vanes extending into the fluid space of the 'QWWOU'.

3. A hydraulic coupling for transmitting power from a driving to a driven shaft, comprising, an outer casing on one shaft forming a fluid reservoir, an inner casing on the other shaft 5 rotarlly mounted in the outer casing, a series of intercommunicating radially disposed cylinders and pistons in the inner casing forming an enclosed pressure zone within the reservoir, a valve controlling intercommunication between the cylinders, a symmetrical cam on the outer casing, rollers on the pistons engaging the symmetrical cam whereby the pistons are reciprocated in rotary balance, non-return replenishment valves in the cylinder walls located radially within the piston travel, axial bores in the stems of said valves open to the reservoir, and transverse bores in the valves communicating with the axial bores which when the valves open permit fluid to pass from the outer reservoir to the go inner pressure zone.

4. In a hydraulic coupling as claimed in claim 1, a symmetrical oval or two-peak cam on the outer casing, and an even number 0! pistons greater than four in the inner casing.

5. A hydraulic coupling for transmitting power from a driving to a driven shaft, comprising, an outer casing on one shaft forming a fluid reservoir, an inner casing on the other shaft rotarily mounted in the outer casing, a relief duct on the inner casing near the rotational axis thereof and communicating with the inner reservoir, a series of intercommunicating radially disposed cylinders and pistons in the inner casing forming an enclosed pressure zone within the reservoir, a valve controlling intercommunication between the cylinders, a symmetrical cam on the outer casing, rollers on the pistons engaging the symmetrical cam whereby the pistons are reciprocated in rotary balance, and nonreturn valves on the inner casing adapted to open and permit fluid to pass from the outer reservoir to the inner pressure zone to replenish such zone when leakage occurs therein.

6. A hydraulic coupling for transmitting power from a driving to a driven shaft comprising, an outer casing on one shaft forming a fluid reservoir, an inner casing on the other shaft rotarily mounted in the outer casing, a series of intercommunicating radially disposed cylinders and pistons in the inner casing forming an enclosed pressure zone within the reservoir, a cavity in the inner casing, ducts in the inner casing leading from the cavity to the cylinders and by which they intercommunicate, a rotary ported valve in the cavity for controlling pulsations of fluid between the cylinders, a spindle for operating said valve, a slot in said spindle, slots in the opposite flat faces of the valve, keys passing through the slots and engaging the opposite faces of the valve, a symmetrical cam formed on the outer casing, rollers on the pistons engaging the symmetrical cam whereby the pistons are reciprocated in rotary balance, and non-return valves on the inner casing adapted to open and permit fluid to pass from the outer reservoir to the inner pressure zone to replenish such zone only when leakage occurs therein.

WILLIAM FRASER. 

